ANALOG MODELING OF DETACHMENT FAULT SYSTEMS AND CORE COMPLEXES

Laboratory experiments on detachment systems in an extending brittle-d uctile crust showed that the rise of a domal core complex in the ducti le layer required that shear be localized above a soft inclusion in a laterally inhomogeneous ductile layer. Gravity spreading of models con sisting of laterally homogeneous layers of sand over ductile silicone resulted in homogeneous patterns of tilted blocks. Systematic and repr oducible patterns of our models simulate features classically observed in natural detachment systems. The extensional system is composed pri ncipally of a main detachment fault with a convex-upward shape and at least one listric accommodation fault, which facilitates progressive s teepening of the footwall during the rise of the core complex. All fau lts begin as steeply dipping normal faults that rotate to low dips dur ing extension.